Purification and Properties of Bacterial Chondroitinases and Chondrosulfatases

Rerouting of fibroblast growth factor 2 to the classical secretory pathway results in post-translational modifications that block binding to heparan sulfate proteoglycans

FGF-2 is a proangiogenic growth factor secreted by unconventional means. It is unknown why FGF-2 takes an ER/Golgi-independent secretory route. We find that secretion of FGF-2 via the ER/Golgi system causes post-translational modifications that prevent binding to heparan sulfate proteoglycans (HSPGs), an interaction that is critically important for both FGF-2 storage and signal transduction. This loss of function is due to artificial O-glycosylation mainly resulting in the addition of glycosaminoglycan chains of the chrondroitin sulfate type. Our findings suggest that the unconventional mechanism of FGF-2 export is an ancient pathway of protein secretion that, in the course of evolution, has been kept due to the inability of the classical secretory pathway to export FGF-2 in a functional form.

Articular cartilage tensile integrity: modulation by matrix depletion is maturation-dependent

Articular cartilage function depends on the molecular composition and structure of its extracellular matrix (ECM). The collagen network (CN) provides cartilage with tensile integrity, but must also remodel during growth. Such remodeling may depend on matrix molecules interacting with the CN to modulate the tensile behavior of cartilage. The objective of this study was to determine the effects of increasingly selective matrix depletion on tensile properties of immature and mature articular cartilage, and thereby establish a framework for identifying molecules involved in CN remodeling. Depletion of immature cartilage with guanidine, chondroitinase ABC, chondroitinase AC, and Streptomyces hyaluronidase markedly increased tensile integrity, while the integrity of mature cartilage remained unaltered after depletion with guanidine. The enhanced tensile integrity after matrix depletion suggests that certain ECM components of immature matrix serve to inhibit CN interactions and may act as modulators of physiological alterations of cartilage geometry and tensile properties during growth/maturation.

Identification of a novel chondroitin hydrolase in Caenorhabditis elegans

Hyaluronidases have been postulated to be the enzyme acting at the initial step of chondroitin sulfate (CS) catabolism in vivo. Since chondroitin (Chn) but not hyaluronic acid (HA) has been detected in Caenorhabditis elegans, the nematode is a good model for elucidating the mechanism of the degradation of CS/Chn in vivo. Here we cloned the homolog of human hyaluronidase in C. elegans, T22C8.2. The Chn-degrading activity in vitro was first demonstrated when it was expressed in COS-7 cells. The enzyme cleaved preferentially Chn. CS-A and CS-C were also depolymerized but to lesser extents, and HA was hardly degraded. In order of preference, the substrates ranked Chn >> CS-A > CS-C >> HA. The products of the degradation of Chn by the enzyme were characterized by anion-exchange high performance liquid chromatography and delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The structure of the major component in the digest was determined as GlcUAbeta1-3GalNAcbeta1-4GlcUAbeta1-3GalNAc, where GlcUA and GalNAc represent D-glucuronic acid and N-acetyl-D-galactosamine, respectively, indicating that this enzyme is a Chn hydrolase, an endo-beta-galactosaminidase specific for Chn. Investigation of the effects of pH on the activity revealed the optimum pH of Chn hydrolase to be 6.0. Since Chn in C. elegans has been demonstrated to play critical roles in cell division, Chn hydrolase possibly regulates the function of Chn in vivo. This is the first demonstration of a Chn hydrolase in an animal.

Adult bone marrow-derived mononuclear cells expressing chondroitinase AC transplanted into CNS injury sites promote local brain chondroitin sulphate degradation

Injury to the CNS of vertebrates leads to the formation of a glial scar and production of inhibitory molecules, including chondroitin sulphate proteoglycans. Various studies suggest that the sugar component of the proteoglycan is responsible for the inhibitory role of these compounds in axonal regeneration. By degrading chondroitin sulphate chains with specific enzymes, denominated chondroitinases, the inhibitory capacity of these proteoglycans is decreased. Chondroitinase administration involves frequent injections of the enzyme at the lesion site which constitutes a rather invasive method. We have produced a vector containing the gene for Flavobacterium heparinum chondroitinase AC for expression in adult bone marrow-derived cells which were then transplanted into an injury site in the CNS. The expression and secretion of active chondroitinase AC was observed in vitro using transfected Chinese hamster ovarian and gliosarcoma cells and in vivo by immunohistochemistry analysis which showed degraded chondroitin sulphate coinciding with the location of transfected bone marrow-derived cells. Immunolabelling of the axonal growth-associated protein GAP-43 was observed in vivo and coincided with the location of degraded chondroitin sulphate. We propose that bone marrow-derived mononuclear cells, transfected with our construct and transplanted into CNS, could be a potential tool for studying an alternative chondroitinase AC delivery method.

Structural analysis of bikunin glycosaminoglycan

The structure of an intact glycosaminoglycan (GAG) chain of the bikunin proteoglycan (PG) was analyzed using a combined top-down and bottom-up sequencing strategy. PGs are proteins with one or more linear, high-molecular weight, sulfated GAG polysaccharides O-linked to serine or threonine residues. GAGs are often responsible for the biological functions of PGs, and subtle variations in the GAG structure have pronounced physiological effects. Bikunin is a serine protease inhibitor found in human amniotic fluid, plasma, and urine. Bikunin is posttranslationally modified with a chondroitin sulfate (CS) chain, O-linked to a serine residue of the core protein. Recent studies have shown that the CS chain of bikunin plays an important role in the physiological and pathological functions of this PG. While no PG or GAG has yet been sequenced, bikunin, the least complex PG, offers a compelling target. Electrospray ionization Fourier transform-ion cyclotron resonance mass spectrometry (ESI FTICR-MS) permitted the identification of several major components in the GAG mixture having molecular masses in a range of 5505-7102 Da. This is the first report of a mass spectrum of an intact GAG component of a PG. FTICR-MS analysis of a size-uniform fraction of bikunin GAG mixture obtained by preparative polyacrylamide gel electrophoresis, allowed the determination of chain length and number of sulfo groups in the intact GAGs.

Chondrotinase ABC enhances axonal regeneration across nerve gaps

We evaluated the effects of chondroitinase ABC on axonal regeneration across peripheral nerve gaps. We compared axonal regeneration after 15-mm tibial nerve resection and repair with a silicone tube filled with type I collagen gel (negative control group), with a silicone tube filled with type I collagen gel containing chondroitinase ABC at three different concentrations (2.5 units/mL, 5 units/mL, 10 units/mL) (chondroitinase ABC groups), and with an autologous nerve segment (nerve autograft group). Electrophysiological and histological assessments were carried out 12 weeks after surgery. In the electrophysiological study, compound muscle action potentials (CMAPs) and nerve conduction velocities (NCVs) were recorded in all groups except the negative control group. Although both CMAPs and NCVs were highest in the nerve autograft group, there were no significant differences among the three chondroitinase ABC groups in either parameter. Histological findings were consistent with electrophysiological results. Based on these findings, we conclude that topical injection of chondroitinase ABC can significantly increase the critical length of nerve gap repair by tubulization or artificial nerve placement.

Two-dimensional electrophoresis of proteins secreted from articular cartilage

Two-dimensional electrophoresis (2DE) is a powerful method for separation of complex mixtures of proteins. The standard procedure is not, however, well suited to analysis of articular cartilage, which contains high concentrations of proteoglycans, the polyanionic glycosaminoglycan chains of which interfere with isoelectric focusing. We have developed a method for selective removal of proteoglycans by precipitation with cetylpyridinium chloride, after which the residual cartilage proteins are amenable to conventional 2DE analysis. Using this method, reproducible 2D-patterns can be obtained from proteins secreted by articular cartilage. The separated proteins may then be visualized by metabolic radiolabeling and silver staining, digested in gel with trypsin, and identified by tandem mass spectrometry.

Enzymatic removal of hyaluronan affects routing of axons in the mouse optic chiasm

Perturbations of interaction of hyaluronan (HA) with its receptor CD44 cause multiple errors in axon routing at the mouse optic chiasm. To investigate this interaction further on the chiasm routing, we studied the axon routing after enzymatic removal of HA from slice preparations of the optic pathway. Hyaluronidase treatment produced an obvious reduction in midline crossing of the first generated axons in E13 chiasms, but had no influence on routing ofthe uncrossed axons in E15 and E16 slices. These findings support a direct role of HA, acting probably through CD44, on axon decussation during early phase of chiasm development, but argue against a direct function of HA on the turning of uncrossed axons in the mouse optic chiasm.

Two related but distinct chondroitin sulfate mimetope octasaccharide sequences recognized by monoclonal antibody WF6

Chondroitin sulfate (CS) proteoglycans are major components of cartilage and other connective tissues. The monoclonal antibody WF6, developed against embryonic shark cartilage CS, recognizes an epitope in CS chains, which is expressed in ovarian cancer and variably in joint diseases. To elucidate the structure of the epitope, we isolated oligosaccharide fractions from a partial chondroitinase ABC digest of shark cartilage CS-C and established their chain length, disaccharide composition, sulfate content, and sulfation pattern. These structurally defined oligosaccharide fractions were characterized for binding to WF6 by enzyme-linked immunosorbent assay using an oligosaccharide microarray prepared with CS oligosaccharides derivatized with a fluorescent aminolipid. The lowest molecular weight fraction recognized by WF6 contained octasaccharides, which were split into five subfractions. The most reactive subfraction contained several distinct octasaccharide sequences. Two octasaccharides, DeltaD-C-C-C and DeltaC-C-A-D (where A represents GlcUAbeta1-3GalNAc(4-O-sulfate), C is GlcUAbeta1-3Gal-NAc(6-O-sulfate), D is GlcUA(2-O-sulfate)beta1-3GalNAc(6-O-sulfate), DeltaCis Delta(4,5)HexUAalpha1-3GalNAc(6-O-sulfate), and DeltaDis Delta(4,5)HexUA(2-O-sulfate)alpha1-3GalNAc(6-O-sulfate)), were recognized by WF6, but other related octasaccharides, DeltaC-A-D-C and DeltaC-C-C-C, were not. The structure and sequences of both the binding and nonbinding octasaccharides were compared by computer modeling, which revealed a remarkable similarity between the shape and distribution of the electrostatic potential in the two different octasaccharide sequences that bound to WF6 and that differed from the nonbinding octasaccharides. The strong similarity in structure predicted for the two binding CS octasaccharides (DeltaD-C-C-C and DeltaC-C-A-D) provided a possible explanation for their similar affinity for WF6, although they differed in sequence and thus form two specific mimetopes for the antibody.

How does chondroitinase promote functional recovery in the damaged CNS?

A number of recent studies have established that the bacterial enzyme chondroitinase ABC promotes functional recovery in the injured CNS. The issue of how it works is rarely addressed, however. The effects of the enzyme are presumed to be due to the degradation of inhibitory chondroitin sulphate GAG chains. Here we review what is known about the composition, structure and distribution of the extracellular matrix in the CNS, and how it changes in response to injury. We summarize the data pertaining to the ability of chondroitinase to promote functional recovery, both in the context of axon regeneration and the reactivation of plasticity. We also present preliminary data on the persistence of the effects of the enzyme in vivo, and its hyaluronan-degrading activity in CNS homogenates in vitro. We then consider precisely how the enzyme might influence functional recovery in the CNS. The ability of chondroitinase to degrade hyaluronan is likely to result in greater matrix disruption than the degradation of chondroitin sulphate alone.

An immunological study of glycosaminoglycans in the connective tissue of bovine and cod skeletal muscle

The presence of sulfated glycosaminoglycans (GAGs) was demonstrated in the connective tissue of bovine and cod skeletal muscle by histochemical staining using Alcian blue added MgCl(2) (0.06 M and 0.4 M, respectively). For further identification of the sulfated GAGs, a panel of monoclonal antibodies, 1B5, 2B6, 3B3 and 5D4 was used that recognizes epitopes in chondroitin-0-sulfate (C0S), chondroitin-4-sulfate/dermatan sulfate (C4S/DS), chondroitin-6-sulfate (C6S) and keratan sulfate (KS), respectively. Light microscopy and Western blotting techniques showed that in bovine and cod muscle C0S and C6S were primarily localized pericellularly, whereas cod exhibited a more intermittent staining. C4S was expressed around the separate cells and also in the perimysium and myocommata. In contrast to bovine muscle, which hardly expressed highly sulfated KS, cod exhibited a very strong and consistent staining. Western blotting showed that C0S and C6S were mainly associated with proteoglycans (PGs) of high molecular sizes in both species. Contrary to bovine muscle, C4S in cod was associated with molecules of various sizes. Both cod and bovine muscle contained KSPGs of similar sizes as C4S. KSPGs of different sizes and buoyant densities, sensitive to keratanase I and II were found expressed in cod.

Mechanisms of cartilage growth: modulation of balance between proteoglycan and collagen in vitro using chondroitinase ABC

OBJECTIVE

To examine the cartilage growth-associated effects of a disruption in the balance between the swelling pressure of glycosaminoglycans (GAGs) and the restraining function of the collagen network, by diminishing GAG content prior to culture using enzymatic treatment with chondroitinase ABC.

METHODS

Immature bovine articular cartilage explants from the superficial and middle layers were analyzed immediately or after incubation in serum-supplemented medium for 13 days. Other explants were treated with chondroitinase ABC to deplete tissue GAG and also either analyzed immediately or after incubation in serum-supplemented medium for 13 days. Treatment- and incubation-associated variations in tissue volume, contents of proteoglycan and collagen network components, and tensile mechanical properties were assessed.

RESULTS

Incubation in serum-supplemented medium resulted in expansive growth with a marked increase in tissue volume that was associated with a diminution of tensile integrity. In contrast, chondroitinase ABC treatment on day 0 led to a marked reduction of GAG content and enhancement of tensile integrity, and subsequent incubation led to maturational growth with minimal changes in tissue volume and maintenance of tensile integrity at the enhanced levels.

CONCLUSION

The data demonstrate that a manipulation of GAG content in articular cartilage explants can distinctly alter the growth phenotype of cartilage. This may have practical utility for tissue engineering and cartilage repair. For example, the expansive growth phenotype may be useful to fill cartilage defects, while the maturational growth phenotype may be useful to induce matrix stabilization after filling defect spaces.

The differential influence of colocalized and segregated dual protein signals on neurite outgrowth on surfaces

We present an in vitro micropatterning approach in which the density and spatial presentation of two separate protein layers can be independently controlled to form cell stripe assays through (1) the simultaneous application of microcontact printing (microCP) and microfluidic network (microFN) patterning to generate alternating stripes of pure single protein layers or (2) through microCP onto a pre-adsorbed homogeneous protein layer to generate alternating single and dual protein stripes. This approach enabled the creation of choice boundaries in which protein-protein interactions were limited and the effects of spatially segregated or colocalized dual protein signals on model primary neuronal behavior could be readily interrogated and compared on both glass and tissue culture polystyrene substrates. Dorsal root ganglion (DRG) cell body attachment was dictated largely by non-specific cell adhesion interactions and interactions between the guidance molecules laminin and aggrecan were insufficient to explain aggrecan inhibition on neurite outgrowth. The presentation of a specific laminin epitope stabilized by interactions with aggrecan and destabilized by microCP was a strong predictor of neurite promoting activity. These observations provide evidence that aggrecan is intrinsically inhibitory and that laminin-aggrecan interactions do not diminish laminin growth promoting properties.

Improved method for analysis of glycosaminoglycans in glycosaminoglycan/protein mixtures: Application in Cohn–Oncley fractions of human plasma

BACKGROUND

Glycosaminoglycans are found in human tissues including plasma. They encompass chondroitin sulphates, heparan sulphate/heparin, hyaluronic acid, and keratan sulphate. Glycosaminoglycans, in particular heparan sulphate and heparin, are strongly associated with plasma proteins, so that their purification results quite difficult.

METHODS

In order to study the distribution of glycosaminoglycans in plasma subfractions, we developed a novel method that allows their identification even if they were still associated with proteins or peptides. Plasma was fractionated following the procedure of Cohn-Oncley, and each fraction was treated with proteases. After centrifugation, glycosaminoglycan/protein complexes in the supernatant were analysed using a modified cellulose acetate electrophoresis which allowed identification of glycosaminoglycans in mixtures of glycosaminoglycans/proteins.

RESULTS

Chondroitin sulphate was recovered in cryoprecipitate and in all Cohn-Oncley fractions. Glycosaminoglycans belonging to the class of heparan sulphate/heparin, however, were recovered in the cryoprecipitate and in fractions I and IV-1, and, in smaller amount, in fraction II+III.

CONCLUSIONS

Since the largest amount of plasma proteins is partitioned in Factions II+III and V, these results demonstrate that heparan sulphate/heparin are not randomly distributed in Cohn-Oncley fractions and are associated with certain plasma proteins. This association might play a role in the physiological function of heparan sulphate/heparin, regulating hemostasis and atherogenesis.

Alteration of matrix glycosaminoglycans diminishes articular chondrocytes' response to a canonical Wnt signal

OBJECTIVE

Although Wnt signaling is a key regulator of the chondrocyte life cycle during embryonic development, little is known about Wnt activity in articular cartilage. Recent studies have suggested an association between excess signaling through the canonical Wnt pathway and osteoarthritis (OA). Genetic and in vitro studies with Drosophila have shown that signaling by the orthologous protein, Wingless (Wg), is regulated by glycosaminoglycans (GAGs) found at the cell surface. The objective of this study was to determine whether alteration in GAG sulfation or matrix content, such as that occurs in OA cartilage, would affect articular chondrocytes' response to a canonical Wnt stimulus.

METHODS

Cells were isolated from shoulder joints of young calves (bovine articular chondrocytes, bACs) and from human cartilage (human articular chondrocytes, hACs) discarded during total knee replacement for OA. Conditioned media from a cell line that is stably transfected with Wnt3a was used as a source of Wnt protein that activates the canonical signaling pathway. Conditioned media from the parental cell line was used as a control. beta-catenin levels were measured by immunoblot. In some experiments, chondrocyte cultures were treated with sodium chlorate (NaClO3) to inhibit GAG sulfation, or with chondroitinase ABC (ChABC) to digest chondroitin sulfate (CS) in the matrix.

RESULTS

Cultured bACs showed low steady-state levels of beta-catenin that increased upon stimulation with Wnt3a. A decrease in either GAG sulfation or CS content diminished bACs' response to Wnt3a (approximately 40% and 37% of control, respectively). Similar effects on the response to Wnt3a via beta-catenin were observed for cultured hACs with undersulfation of GAGs (16% of control) and decreased CS content (20% of control).

CONCLUSION

This study demonstrates that articular chondrocytes respond to canonical Wnt stimulation, and that reduced sulfation or CS content diminishes that response.

Conformational Studies on Five Octasaccharides Isolated from Chondroitin Sulfate Using NMR Spectroscopy and Molecular Modeling

Chondroitin sulfate proteoglycans (CS-PG) are involved in the regulation of the central nervous system in vertebrates due to their presence on cell surfaces and in the extracellular matrix of tissues. The CS moieties are built up from repeating -4)GlcA(beta1-3)GalNAc(beta1- disaccharide units, partly O-sulfated at different positions. The presence of the disulfated disaccharide D-unit, GlcA2S(beta1-3)GalNAc6S, in the CS moiety of the proteoglycan DSD-1-PG/phosphacan, correlates with neurite outgrowth promotion. The binding of monoclonal antibody (mAb) 473HD to DSD-1-PG, reducing neuronal stimulation, is inhibited by shark cartilage CS-D. CS-D is also recognized by two other mAbs, MO-225 and CS-56. Conformational studies were performed using NMR spectroscopy and molecular modeling on five octasaccharides isolated from shark cartilage CS-D. These octasaccharides present different binding properties toward the three mAbs. The combination of the experimental and theoretical approaches revealed that the sulfate group at position 2 of GlcA in disaccharide D and the presence of an exocyclic negative tail in disaccharides C [GlcA(beta1-3)GalNAc6S] and DeltaC [Delta4,5HexA(alpha1-3)GalNAc6S] are important for antibody recognition.

Fibromodulin interactions with type I and II collagens

Fibromodulin is a keratan-sulfate small leucine-rich proteoglycan (SLRP) regulating collagen I and II fibril formation. In vivo studies suggest that, alongside decorin, fibromodulin plays an important role in the maintenance of mature tissues. To characterize fibromodulin/decorin differences in binding to type I and II collagen, we tested the collagen CNBr peptides in solid-phase assays. Only one peptide from collagen II and several peptides from collagen I interacted with fibromodulin, pointing to multiple binding sites in the collagen I molecule. By Scatchard-type analysis, the fibromodulin molecule showed only one class of binding sites for collagen I and both low and high affinity (classes of) binding sites for collagen II. Lys/Hyl residues in both collagens are essential for the interaction. Fibril formation assays showed the concomitant presence of fibromodulin and decorin in fibrils and a cumulative inhibitory effect. In solid-phase assays decorin seems to inhibit fibromodulin binding, whereas the contrary does not occur. We found fibromodulin and decorin have similarities and differences that may represent the biochemical basis of redundancy in SLRP function with compensation between different (classes of) SLRPs.

Identification of the Origin of Chondroitin Sulfate in "Health Foods"

Twelve "health foods" products containing chondroitin sulfate (CS) were purchased from the Japanese market and the origin of the CS was investigated by conducting disaccharide compositional analysis after enzymatic depolymerization and by 1H-NMR spectroscopy. Nine of the 12 products had labels indicating that the origin of the CS was shark cartilage. However, two of them were found to contain mammalian CS. Next, we compared the ratio of the sulfate group to the galactosamine residue after the acid hydrolysis of CS. The results suggest that all of the CS from sharks had a ratio of more than 1.0, while the CS from mammals had a ratio of less than 1.0. Since this comparative analysis does not require expensive purified enzyme, it would be an economical way to identify the origin of CS in "health foods." Being able to determine the origin of the ingredients in natural products is very important for ensuring their quality, safety, and efficacy. Therefore, we think that regulatory requirements for accurately indicating the origin of "health foods" and effective enforcement of these requirements are needed.

Matrix metalloproteinases and proteoglycans in axonal regeneration

After an injury to the adult mammalian central nervous system (CNS), a variety of growth-inhibitory molecules are upregulated. A glial scar forms at the site of injury and is composed of numerous molecular substances, including chondroitin sulfate proteoglycans (CSPGs). These proteoglycans inhibit axonal growth in vitro and in vivo. Matrix metalloproteinases (MMPs) can degrade the core protein of some CSPGs as well as other growth-inhibitory molecules such as Nogo and tenascin-C. MMPs have been shown to facilitate axonal regeneration in the adult mammalian peripheral nervous system (PNS). This review will focus on the various roles of proteoglycans and MMPs within the injured nervous system. First, we will present a general background on the injured central nervous system and explore the roles that proteoglycans play in the injured PNS and CNS. Second, we will discuss the various functions of MMPs within the injured PNS and CNS. Special attention will be paid to the possibility of how MMPs might modify the growth-inhibitory extracellular environment of the injured adult mammalian spinal cord and facilitate axonal regeneration in the CNS.

Occurrence of a nonsulfated chondroitin proteoglycan in the dried saliva of Collocalia swiftlets (edible bird's-nest)

Despite their wide occurrence, proteoglycans (PGs) have never been isolated from the saliva of higher animals. We found that the Collocalia glycoproteins isolated from edible birds'-nests (the dried forms of regurgitated saliva of male Collocalia swiftlets) were rich in a PG containing nonsulfated chondroitin glycosaminoglycans (GAGs). We have devised a method to isolate a PG from the water extract of the white nest built by Aerodramus fuciphagus (white nest swiftlets) with a yield of 2-mg PG per gram nest. This PG contained 83% of carbohydrates, of which 79% were GalNAc and GlcUA (D-glucuronic acid) in an equimolar ratio. By using chondroitin AC lyase, the structure of GAGs in this PG was established to be chondroitin ( --> 4GlcUAbeta1 --> 3GalNAcbeta1 --> )(n) chains. The average molecular mass of the chondroitin chain was estimated to be 49 kDa by gel filtration. We have isolated a linkage region hexasaccharide, DeltaHexUAalpha1 --> 3GalNAcbeta1 --> 4GlcUAbeta1 --> 3Galbeta1 --> 3Galbeta1 --> 4Xyl, from this PG by chondroitinase ABC digestion to show that the GAGs in this PG are also linked to the core protein through the common tetrasaccharide linker, GlcUAbeta1 --> 3Galbeta1 --> 3Galbeta1 --> 4Xyl, found in various PGs. As water was not effective in extracting uronic acid-containing glycoconjugates from the black nest built by black nest swiftlets (A. maximus), we used 4 M guanidium chloride and anion-exchange chromatography in the presence of urea to extract and isolate about 30 mg of a chondroitin PG preparation from 10 g of the desialylated black nest. As the biological significance of chondroitin is still not well understood, bird's nest should become a convenient source for preparing this unique GAG to study its biological functions.

Insights into the Mechanism of Action of Hyaluronate Lyase

Hyaluronate lyases (HLs) cleave hyaluronan and certain other chondroitin/chondroitin sulfates. Although native HL from Streptococcus agalactiae is composed of four domains, it finally stabilizes after autocatalytic conversion as a 92-kDa enzyme composed of the N-terminal spacer, middle alpha-, and C-terminal domains. These three domains are independent folding/unfolding units of the enzyme. Comparative structural and functional studies using the enzyme and its various fragments/domains suggest a relatively insignificant role of the N-terminal spacer domain in the 92-kDa enzyme. Functional studies demonstrate that the alpha-domain is the catalytic domain. However, independently it has a maximum of only about 10% of the activity of the 92-kDa enzyme, whereas its complex with the C-terminal domain in vitro shows a significant enhancement (about 6-fold) in the activity. It has been previously proposed that the C-terminal domain modulates the enzymatic activity of HLs. In addition, one of the possible roles for calcium ions was suggested to induce conformational changes in the enzyme loops, making HL more suitable for catalysis. However, we observed that calcium ions do not interact with the enzyme, and its role actually is in modulating the hyaluronan conformation and not in the functional regulation of enzyme.

Transforming growth factor-beta as a key molecule triggering the expression of versican isoforms v0 and v1, hyaluronan synthase-2 and synthesis of hyaluronan in malignant osteosarcoma cells

Versican, a large sized chondroitin-sulphate proteoglycan (PG), and its binding partner, hyaluronan (HA), are extracellular matrix (ECM) components that play an essential role in transformed cell behavior. Expression of certain versican isoforms has been implicated in cell migration and proliferation of cancer cells and, on the other hand, disruption of HA synthesis by inhibiting hyaluronan synthase-2 (HAS2) expression in osteosarcoma cells by suppressing cell proliferation, invasiveness and motility. Considering that growth factors, such as TGF-beta, bFGF and PDGF-BB, are important regulators for the expression of the ECM macromolecules, in this study we examined the effect of these growth factors on the expression of the various versican isoforms, HA synthases as well as HA synthesis by MG-63 osteosarcoma cells and normal human osteoblastic periodontal ligament cells (hPDL). Real-time PCR and metabolic labelling followed by fine HPLC analysis coupled to radiochemical detection were the methods utilized. It was found that, contrary to normal hPDL cells, osteosarcoma MG-63 cells do not constitutively express the versican isoforms V0 and V1. Exogenous addition of TGF-beta2 stimulated the versican transcript levels mainly by forcing osteosarcoma cells to express V1 and V0 isoforms. PDGF-BB and bFGF had only minor effects in these cells. In hPDL cells a strong stimulation of the V3 transcript by all growth factors was observed. TGF-beta2 was also the major stimulator of HAS2 isoform expression as well as hyaluronan synthesis in osteosarcoma cells, while PDGF-BB exerted dominant influence on HAS2 isoform expression and hyaluronan biosynthesis by osteoblasts. The obtained results show for the first time that TGF-beta2 triggers the malignant phenotype pattern of versican and hyaluronan expression in human osteosarcoma cells and indicate that this growth factor may account for the metastatic potential of these cells.

Porcine circovirus 2 uses heparan sulfate and chondroitin sulfate B glycosaminoglycans as receptors for its attachment to host cells

Monocyte/macrophage lineage cells are target cells in vivo for porcine circovirus 2 (PCV2) replication. The porcine monocytic cell line 3D4/31 supports PCV2 replication in vitro, and attachment and internalization kinetics of PCV2 have been established in these cells. However, PCV2 receptors remain unknown. Glycosaminoglycans (GAG) are used by several viruses as receptors. The present study examined the role of GAG in attachment and infection of PCV2. Heparin, heparan sulfate (HS), chondroitin sulfate B (CS-B), but not CS-A, and keratan sulfate reduced PCV2 infection when these GAG were incubated with PCV2 prior to and during inoculation of 3D4/31 cells. Enzymatic removal of HS and CS-B prior to PCV2 inoculation of 3D4/31 cells significantly reduced PCV2 infection. Similarly, when PCV2 virus-like particles (VLP) were allowed to bind onto 3D4/31 cells in the presence of heparin and CS-B, attachment was strongly reduced. Titration of field isolates and low- and high-passage laboratory strains of PCV2 in the presence of heparin significantly reduced PCV2 titers, showing that the capacity of PCV2 to bind GAG was not acquired during in vitro cultivation but is an intrinsic feature of wild-type virus. When Chinese hamster ovary (CHO) cells were inoculated with PCV2, relative percentages of PCV2-infected cells were 27% +/- 8% for HS-deficient and 12% +/- 10% for GAG-deficient cells compared to wild-type cells (100%). Furthermore, it was shown using heparin-Sepharose chromatography that both PCV2 and PCV2 VLP directly interacted with heparin. Together, these results show that HS and CS-B are attachment receptors for PCV2.

Chondroitinase ABC combined with neural stem/progenitor cell transplantation enhances graft cell migration and outgrowth of growth-associated protein-43-positive fibers after rat spinal cord injury

We previously reported that the transplantation of neural stem/progenitor cells (NSPCs) can contribute to the repair of injured spinal cord in adult rats and monkeys. In some cases, however, most of the transplanted cells adhered to the cavity wall and failed to migrate and integrate into the host spinal cord. In this study we focused on chondroitin sulfate proteoglycan (CSPG), a known constituent of glial scars that is strongly expressed after spinal cord injury (SCI), as a putative inhibitor of NSPC migration in vivo. We hypothesized that the digestion of CSPG by chondroitinase ABC (C-ABC) might promote the migration of transplanted cells and neurite outgrowth after SCI. An in vitro study revealed that the migration of NSPC-derived cells was inhibited by CSPG and that this inhibitory effect was attenuated by C-ABC pre-treatment. Consistently, an in vivo study of C-ABC treatment combined with NSPC transplantation into injured spinal cord revealed that C-ABC pre-treatment promoted the migration of the transplanted cells, whereas CSPG-immunopositive scar tissue around the lesion cavity prevented their migration into the host spinal cord in the absence of C-ABC pre-treatment. Furthermore, this combined treatment significantly induced the outgrowth of a greater number of growth-associated protein-43-positive fibers at the lesion epicentre, compared with NSPC transplantation alone. These findings suggested that the application of C-ABC enhanced the benefits of NSPC transplantation for SCI by reducing the inhibitory effects of the glial scar, indicating that this combined treatment may be a promising strategy for the regeneration of injured spinal cord.

Determination of endogenous glycosaminoglycans derived disaccharides in human plasma by HPLC: Validation and application in a clinical study

SB-424323 is a new, orally active anti-thrombotic agent presently in phase-II clinical development, with limited hemorrhagic risk and a unique mechanism of action involving the induction of glycosaminoglycans (GAGs) biosynthesis. The objective of the present study was to develop a simple and rapid high performance liquid chromatography (HPLC) method for determination of endogenous GAGs derived disaccharides in plasma samples from a phase-II clinical study of SB-424323. Sample preparation was a simple heat treatment of the diluted plasma followed by digestion of endogenous GAGs with chondroitinase ABC to yield unsaturated disaccharides, 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-D-galactose (DeltaDi-0S), 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-4-O-sulfo-D-galactose (DeltaDi-4S), and 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-6-O-sulfo-D-galactose (DeltaDi-6S). These disaccharides were recovered and purified using centrifugal filtration through a filter with 3000 molecular weight cut-off along with externally added internal standard 2-acetamido-2-deoxy-3-O-(2-O-sulfo-beta-D-gluco-4-enepyranosyluronic acid)-D-galactose (DeltaDi-UA2S). A gradient reverse phase HPLC separation was developed on a Waters Symmetry C(18) column (4.6 mm x 150 mm, 5 microm) with a gradient mobile phase system consisting of 0.8 mM tetrabutylammonium hydrogen sulfate and 2mM sodium chloride and acetonitrile at a flow rate of 1.0 mL/min. The eluate was monitored with an ultraviolet detector set at 230 nm. Plasma standard curves were linear (r(2)> or =0.994) in the concentration range 1.0-20 microg/mL with a lower limit of quantification (LLOQ) of 1.0 microg/mL for each of the disaccharide. The mean measured quality control (QC) concentrations for the disaccharides deviated from the nominal concentrations in the range of -8.92 to 5.61% and -16.3 to 16.7%, for inter and intra-day, respectively. The inter and intra-day precision in the measurement of QC samples, were in the range of 3.21 to 18.2% relative standard deviation (R.S.D.) and 0.32 to 20.9% R.S.D., respectively. The inter and intra-day precision in the measurement of endogenous GAGs derived disaccharides in human control plasma, were in the range of 5.8 to 15.9% R.S.D. and 1.17 to 7.74% R.S.D., respectively. Stability of the processed samples was confirmed up to 48 h in the auto-sampler. The method is simple, reliable, and easily adaptable to analysis of large number of samples under logistics of a clinical study. The present method has been used to investigate the GAGs levels in the plasma of patients in a phase II clinical study of SB-424323.

Structure of a group A streptococcal phage-encoded virulence factor reveals a catalytically active triple-stranded beta-helix

Streptococcus pyogenes (group A Streptococcus) causes severe invasive infections including scarlet fever, pharyngitis (streptococcal sore throat), skin infections, necrotizing fasciitis (flesh-eating disease), septicemia, erysipelas, cellulitis, acute rheumatic fever, and toxic shock. The conversion from nonpathogenic to toxigenic strains of S. pyogenes is frequently mediated by bacteriophage infection. One of the key bacteriophage-encoded virulence factors is a putative "hyaluronidase," HylP1, a phage tail-fiber protein responsible for the digestion of the S. pyogenes hyaluronan capsule during phage infection. Here we demonstrate that HylP1 is a hyaluronate lyase. The 3D structure, at 1.8-angstroms resolution, reveals an unusual triple-stranded beta-helical structure and provides insight into the structural basis for phage tail assembly and the role of phage tail proteins in virulence. Unlike the triple-stranded beta-helix assemblies of the bacteriophage T4 injection machinery and the tailspike endosialidase of the Escherichia coli K1 bacteriophage K1F, HylP1 possesses three copies of the active center on the triple-helical fiber itself without the need for an accessory catalytic domain. The triple-stranded beta-helix is not simply a structural scaffold, as previously envisaged; it is harnessed to provide a 200-angstroms-long substrate-binding groove for the optimal reduction in hyaluronan viscosity to aid phage penetration of the capsule.

Preparation of the methyl ester of hyaluronan and its enzymatic degradation

A methyl ester of hyaluronan in which the carboxyl groups were fully esterified was prepared using trimethylsilyl diazomethane. This derivative, while not depolymerized by hyaluronan lyases or hyaluronan hydrolases, was a substrate for both chondroitin ACI lyase (EC 4.2.2.5) from Flavobacterium heparinum and chondroitin ACII lyase (EC 4.2.2.5) from Arthrobacter aurescens. The major product isolated in these depolymerization reactions was methyl alpha-L-threo-hex-4-enepyranosyluronate-(1-->3)-2-acetamido-2-deoxy-alpha,beta-D-glucopyranoside as determined by 1H NMR spectroscopy and MALDITOF mass spectrometry.

Gene cloning and functional analysis of glycosaminoglycan-degrading enzyme chondroitin AC lyase from Flavobacterium columnare G4

The chondroitin AC lyase gene, cslA, was cloned for the first time from the fish bacterial pathogen F. columnare G4. From the first transcription initiation site, the cslA extends 2620 nucleotides to the end of the 3' region. The open reading frame of cslA transcript has 2286 nucleotides encoding 762 amino acids with a 16 residues long signal peptide at the N-terminus. The gene, cslA was then successfully expressed in Escherichia coli and recombinant chondroitin AC lyase, rChonAC was purified, with its lytic activity analyzed. Zymography analysis copolymerized with chondroitin sulphate revealed the lytic activity of rChonAC and also the crude native ChonAC isolated from periplamic space of cultured F. columnare G4. The low level of lytic activity observed in crude native ChonAC may be due possibly to the low level of expression of this gene in the cultured condition. The expression and the role of this virulence factor is of interest for further research on the pathogenesis of F. columnare.

Calcified Matrix Production by SAOS-2 Cells Inside a Polyurethane Porous Scaffold, Using a Perfusion Bioreactor

The repair and regeneration of damaged or resected bone are problematic. Bone autografts show optimal skeletal incorporation, but often bring about complications. Hence, there is increasing interest in designing new biomaterials that could potentially be used in the form of scaffolds as bone substitutes. In this study we used a hydrophobic cross-linked polyurethane in a typical tissue-engineering approach, that is, the seeding and in vitro culturing of cells within a porous scaffold. The polyurethane porous scaffold had an average pore diameter of 624 microm. Using a perfusion bioreactor, we investigated the effect of shear stress on SAOS-2 human osteoblast proliferation and calcified matrix production. The physical, morphological, and compressive properties of the polyurethane foam were characterized. At a scaffold perfusion rate of 3 mL/min, in comparison with static conditions without perfusion, we observed 33% higher cell proliferation; higher secretion of osteopontin, osteocalcin, decorin, and type I collagen (9.16-fold, 71.9-fold, 30.6-fold, and 18.12-fold, respectively); and 10-fold increased calcium deposition. The design of the bioreactor and the design of the polyurethane foam aimed at obtaining cell colonization and calcified matrix deposition. This cultured biomaterial could be used, in clinical applications, as an osteoinductive implant for bone repair.

Dynamic mechanical characteristics of intact and structurally modified bovine pericardial tissues

Bovine pericardium (BP) is a source of natural biomaterials with a wide range of clinical applications. In the present work we studied the dynamic mechanical behavior of BP in native form and under specific enzymatic degradation with chondroitinase ABC extracted a 17% of the total glycosaminoglycans (GAGs). The GAGs content of native BP was composed mainly from hyaluronan, chondroitine sulfate and dermatan sulfate. Dynamic tensile mechanical testing of BP in the frequency range 0.1-20 Hz demonstrated its viscoelastic nature. The storage modulus was equal to 6.5 (native) and 5.5 (degraded) MPa initially, increased in the region nearby 1 Hz by about 15%. This was related with physical resonance mechanisms activated in this frequency region. The high modulus (modulus of the high linear phase of stress-strain) was equal to 14 (native) and 10 (degraded) MPa, dropped at high frequencies to 7 and 5 Mpa, respectively. The damping, expressed by the hysteresis, was equal to 20% of the loading energy, changed exponentially with the frequency to 30% at 20 Hz. It seemed that of the elastic mechanical parameters, the storage modulus and the high modulus were even slightly dropped as a result of degradation. As a final conclusion, there was evident that GAGs may play a non-negligible role in the dynamic mechanical behavior of BP and, probably in other soft tissue biomechanics. It is suggested that the GAGs content may be considered during the design and chemical modification of biomaterials based on BP and other soft tissues.

Sulfated glycosaminoglycans in the extracellular matrix of muscle tissue in Atlantic cod (Gadus morhua) and Spotted wolffish (Anarhichas minor)

Two species of commercially important cold water fish were investigated for content of sulfated glycosaminoglycans (GAGs) in muscle tissue by use of in vivo 35S-sulfate labeling combined with different digestions (papain, chondroitinase ABC, keratanase and nitrous acid treatment), DEAE chromatography, SDS-PAGE and histology techniques. The species investigated in this study have different gaping properties. The non-gaping species, spotted wolffish (Anarhichas minor), contained 3-4 times more 35S-sulfated anionic components than the gaping species, Atlantic cod (Gadus morhua). The higher level of sulfation in wolffish was supported by light microscopy studies using Alcian blue staining with different concentrations of MgCl2 as critical electrolyte. Furthermore, the muscular connective tissue in the non-gaping species was dominated by chondroitin sulfate (CS)/dermatan sulfate (DS), whereas the gaping species was more dominated by heparan sulfate (HS). Moreover, structural differences were observed in the junctions between the myofibers, which were more pronounced in the wolffish. The histological studies revealed that the basement membrane area was rich in acidic mucopolysaccharides in both species.

Modulation of collagen fibrillogenesis by dentinal proteoglycans

Studies have identified different pools of proteoglycan (PG) species present within the unmineralized matrix of the predentine, the transitional phase at the predentine-dentine interface and the mineralized dentine. These PGs alter with respect to the chemical nature of their glycosaminoglycan (GAG) chains and as a result of extracellular processing of the macromolecule in the matrix. The present study has examined the influence of the PGs isolated from these phases and the influence of the attached GAG chains, upon their ability to control collagen fibrillogenesis. PGs isolated from the three phases were characterized and determined to contain a mixture of decorin and biglycan. Results have indicated that predentine PGs, which are substituted with a higher proportion of dermatan sulfate, significantly delayed fibril formation while ultimately promoting the formation of thicker fibrils. Removal of the GAG chains further delayed fibrillogenesis, leading to the formation of thinner fibrils, compared with the collagen-only control. PGs isolated from predentine-dentine, which contained a higher proportion of chondroitin sulfate, also significantly delayed fibrillogenesis, resulting in thicker collagen fibrils. GAG chains attached to the predentine-dentine interface PGs played a role in the timing of fibrillogenesis with fibril formation initiated at the same time as the collagen control, but yielding thicker fibrils. Dentine PGs significantly inhibited fibrillogenesis and fibril thickness over concentrations of 50-25 microg/mL protein. In conclusion, the PGs isolated from the distinct phases have indicated differing roles in the orchestrated organization of the extracellular matrix during dentinogenesis, with roles for both the core protein and attached GAG chains indicated.

Sulfatases: Structure, Mechanism, Biological Activity, Inhibition, and Synthetic Utility

Sulfatases, which cleave sulfate esters in biological systems, play a key role in regulating the sulfation states that determine the function of many physiological molecules. Sulfatase substrates range from small cytosolic steroids, such as estrogen sulfate, to complex cell-surface carbohydrates, such as the glycosaminoglycans. The transformation of these molecules has been linked with important cellular functions, including hormone regulation, cellular degradation, and modulation of signaling pathways. Sulfatases have also been implicated in the onset of various pathophysiological conditions, including hormone-dependent cancers, lysosomal storage disorders, developmental abnormalities, and bacterial pathogenesis. These findings have increased interest in sulfatases and in targeting them for therapeutic endeavors. Although numerous sulfatases have been identified, the wide scope of their biological activity is only beginning to emerge. Herein, accounts of the diversity and growing biological relevance of sulfatases are provided along with an overview of the current understanding of sulfatase structure, mechanism, and inhibition.

Binding of von Willebrand factor to the small proteoglycan decorin

The small proteoglycan decorin plays an important role in the organisation of the extracellular matrix by binding to several components, including collagen and fibronectin. In this work, we report the dose-dependent and saturable interaction of decorin with the adhesive glycoprotein, von Willebrand factor (VWF). This interaction was mediated by the glycosaminoglycan side chain of decorin and was critically regulated by the degree of sulfation, but not by the amount of iduronic acid. Both chondroitin sulfate and dermatan sulfate, in addition to heparin, were found to bind VWF equally well. Although soluble decorin prevented VWF binding to heparin, purified VWF-A1 domain failed to interact with the proteoglycan. These results identify VWF as a new partner for the small proteoglycan, decorin, in the structural organisation of the extracellular matrix.

Extracellular Mycobacterial DNA-binding Protein 1 Participates in Mycobacterium-Lung Epithelial Cell Interaction through Hyaluronic Acid

Mycobacterium tuberculosis infects not only host macrophages but also nonprofessional phagocytes, such as alveolar epithelial cells. Glycosaminoglycans (GAGs) are considered as the component of mycobacterial adherence to epithelial cells. Here we show that extracellularly occurring mycobacterial DNA-binding protein 1 (MDP1) promotes mycobacterial infection to A549 human lung epithelial cells through hyaluronic acid (HA). Both surface plasmon resonance analysis and enzyme-linked immunosorbent assay revealed that MDP1 bound to HA, heparin, and chondroitin sulfate. Utilizing synthetic peptides, we next defined heparin-binding site of 20 amino acids from 31 to 50 of MDP1, which is responsible for the specific DNA-binding site of MDP1. MDP1 bound to A549 cells, and exogenous DNA and HA interfered with the interaction. The binding was also abolished by treatment of A549 cells with hyaluronidase, suggesting that HA participates in the MDP1-A549 cell interaction. Adherence of bacillus Calmette-Guérin (BCG) and M. tuberculosis to A549 cells was inhibited by addition of HA, DNA, and anti-MDP1 antibody, showing that MDP1 participates in the interaction between mycobacteria-alveolar epithelial cells. Simultaneous treatment of intratracheal BCG-infected mice with HA reduced the growth of BCG in vivo. Taken together, theses results suggest that HA participates in Mycobacterium-lung epithelium interaction and has potential for therapeutic and prophylactic interventions in mycobacterial infection.

Dentinal proteoglycans demonstrate an increasing order of affinity for hydroxyapatite crystals during the transition of predentine to dentine

The transition from an unmineralized predentine to a mineralized dentine involves a variety of molecular extracellular matrix interactions and protein degradation events. Previous studies have identified that different pools of proteoglycan (PG) species are present within the matrix of the predentine, the transitional phase at the predentine-dentine border, and the mineralized dentine. These PGs alter with respect to the chemical nature of the glycosaminoglycan (GAG) chain and as a result of extracellular processing of the macromolecule in the matrix. This study has examined the hydroxyapatite (HAP) binding affinity of the PGs isolated from these phases and the influence of the attached GAG chains upon their binding characteristics. PGs isolated from the three phases were characterized to contain a mixture of decorin and biglycan, substituted with chondroitin sulfate GAG chain(s). Maximal binding for dentine PGs onto HAP was achieved at 15.60 microg/ml protein and for predentine-dentine interface PGs at 0.125 mg/ml. A significantly increasing gradient of affinity was observed moving toward dentine, with dentine PGs exhibiting 19 times greater binding affinity for HAP than predentine PGs and 7.5 times greater affinity than predentine-dentine interface PGs. Removal of the GAG chains from dentine PGs significantly reduced binding affinity for HAP but did not influence the number of binding sites. The difference in binding ability observed for the different PG pools gives further support for the involvement of these macromolecules in regulating the transition from predentine to dentine and suggests key roles for the GAG chains in the mineralisation process.

Structural Determination of Five Novel Tetrasaccharides Containing 3-O-Sulfated d-Glucuronic Acid and Two Rare Oligosaccharides Containing a β-d-Glucose Branch Isolated from Squid Cartilage Chondroitin Sulfate E

Oversulfated chondroitin sulfate E (CS-E) derived from squid cartilage exhibits intriguing biological activities, which appear to reflect the biological activities of mammalian CS chains containing the so-called E disaccharide unit [GlcAbeta1-3GalNAc(4,6-O-disulfate)]. Previously, we isolated novel tetra- and hexasaccharides containing a rare GlcA(3-O-sulfate) at the nonreducing end after digestion of squid cartilage CS-E with testicular hyaluronidase. In this study, squid cartilage CS-E was extensively digested with chondroitinase AC-II, which yielded five highly sulfated novel tetrasaccharides and two odd-numbered oligosaccharides (tri- and pentasaccharides) containing D-Glc. Their structures were determined by fast atom bombardment mass spectrometry and (1)H NMR spectroscopy. The results revealed an internal GlcA(3-O-sulfate) residue for all the novel tetrasaccharide sequences, which rendered the oligosaccharides resistant to the enzyme. The results suggest that GlcA(3-O-sulfate) units are not clustered but rather interspersed in the CS-E polysaccahride chains, being preferentially located in the highly sulfated sequences. The predominant structure on the nearest nonreducing side of a GlcA(3-O-sulfate) residue was GalNAc(4-O-sulfate) (80%), whereas that on the reducing side was GalNAc(4,6-O-disulfate) (59%). The structural variety in the vicinity of the GlcA(3-O-sulfate) residue might represent the substrate specificity of the unidentified chondroitin GlcA 3-O-sulfotransferase. The results also revealed a trisaccharide and a pentasaccahride sequence, both of which contained a beta-d-Glc branch at the C6 position of the constituent GalNAc residue. Approximately 5 mol % of all disaccharide units were substituted by Glc in the CS-E preparation used.